This invention generally relates to seals for universal joints and in particular to an improved seal which permits limited relative movement between the trunnion and bearing cup and forms a static seal between the trunnion and the bearing cup.
Universal joints are structures which are well known and usually include a cross member having a central body portion with four turnings extending outwardly therefrom. The trunnions extend at right angles relative to one another and lie in a single plane. A central bore is provided in each trunnion forming an opening in the end of the trunnion opposite the central body portion. A hollow cylindrical bearing cup, closed at one end, is disposed over the open end of each of the trunnions. Roller bearings are provided between each of the bearing cups and its associated trunnion such that the bearing cups are rotatably mounted thereon. It is known to provide the open ends of the bearing cups with elastomeric seals which are typically positioned between the trunnion and bearing cup to form a seal therebetween. Normally, the seals provide for complete rotational movement between the trunnion and the bearing cup. Because complete relative movement is provided for, there are compromises in the seal design which permit some slight leakage of lubricant past the seals. Additionally, such seals must resist the entry of contaminants into the bearings. One prior art configuration, commonly known as a lip seal, has been used to accomplish both tasks.
This seal has the disadvantage that while it is possible to initially lubricate the universal joint by passing lubricant over the sealing lip. Once these lips run dry they will not receive any further supply of lubricant. Thus, the sealing lip will wear out due to the lack of lubricant.
Another problem that occurs in the assembly process of the seal between the trunnion and bearing cup is that lubricant is typically applied to the bearing cup and roller bearings prior to assembly with the trunnion. This procedure can cause air to become trapped within the sealed bearing cavity resulting in a build-up of pressure in the bearing cavity during assembly. A pressure build-up in the sealed region can press out the seal which can cause the loss of lubricant and ingress of contaminants, resulting in bearing failure.
Furthermore, during operation of the universal joint, heat is generated by the bearings and this causes the lubricant, trapped air or moisture to increase in temperature. Because lubricants are primarily composed of a mixture of various hydrocarbons, some hydrocarbons can form gases as temperatures increase. These gases plus any trapped air or moisture cause the pressure in the sealed bearing cavity to increase. If this pressure increase is not vented, the seal can be pressed out. This condition can cause bearing failure by permitting the loss of lubricant and the ingress of contaminants.
It is an object of the invention to provide a static elastomeric seal between the trunnion and bearing cup and permit limited rotational or relative movement between the trunnion and bearing cup.
It is a further object to provide a flexible rubber web between the trunnion and bearing cup and yet provide a static seal against the trunnion and a static seal against the bearing cup.
It is still a further object of the present invention to provide a static seal against the trunnion and a static seal against the bearing cup which provides for limited relative movement between the trunnion and bearing cup and which permits purging of trapped air in the lubricant cavity during assembly.
An additional object is to provide an elastomeric rubber web between the trunnion and bearing cup and permit purging of pressure out of the lubricant cavity to prevent seal blow-out.
Still another object of the present invention is to provide static seals against the trunnion and bearing cup, a web between the trunnion and bearing cup and an excluder seal to prevent contamination from entering the main seal.
The seal for a universal joint which consists of a trunnion and a bearing cup in spaced relation to the trunnion. The trunnion and bearing cup further define a cavity for retaining lubricant therein. The seal includes an inner portion, an outer portion and a flexible web portion. The inner portion is adjacent to the trunnion. The outer portion is adjacent to the bearing cup. The flexible web portion permits limited movement of the trunnion relative to the bearing cup. Optionally, the elastomer member has a lip portion so that in one predetermined condition, the lip portion forms a barrier to the passage of lubricant from the cavity and in response to a slight increase in pressure within the cavity, the lip separates to prevent an excessive differential from developing across the lip. Upon venting the pressure, the lip returns to sealing contact.
These and other objects and features of the invention will become apparent from the description and especially taken in conjunction with the accompanying drawings illustrating the invention and embodiments.